External Drive Not Detected

So, I installed OMV on my raspberry pi 3 model b, but it does not detect my 2TB external WD My Passport Ultra. At first it did, but I got a few errors when I tried formatting it in OMV so I can place file system on it, so I tried doing in my local machine and gave it the entire drive one partition with Ext4 file system but it still does not detect it. This drive is not the only drive not being detected, none of my thumb drives are either.

Is there a configuration issue I'm missing? Please keep in mind it's raspberry pi 3 model b and it's being powered by a usb cable plugged into a wall outlet adapter - like for a cell phone. Could it be a power issue?

this is 100% a power issue. Your WD is 2,5" disc without external power supply. Which means your pi has to power it through USB. If you want to use this disc, you need an external USB hub with power supply. Also check your wall outlet power supply for the pi, because as subzero already mentioned, you need 5V /2A just to power the pi itself.